1. Field of the Invention
This invention relates to a control system and more particularly to an improved control system most suitable to a fuel injection control of an engine.
2. Description of Related Art
Heretofore, there is a fuel injection system for an internal combustion engine wherein the engine has a fuel injector that injects fuel into an air intake passage so that the injected fuel is mixed with an air charge and then the mixture is admitted into a combustion chamber for combustion. In order to control the fuel injection system, an air fuel ratio (A/F) sensor is provided at an exhaust passage. This sensor is actually, for example, an oxygen (O2) sensor that detects the density of oxygen in emissions whereby the air fuel ratio of the mixture is measured. The fuel injection system is also provided with a feedback control device that controls the amount of fuel injected into the air intake passage based upon the sensed actual air fuel ratio so that the actual air fuel ratio can close to an objective air fuel ratio. Through the control, eventually improvements in the engine performance, emissions and fuel efficiency is expected.
The fuel injection system described above may provide a number of advantages if the amount of intake air (hereunder referred to as xe2x80x9cair amountxe2x80x9d) can be accurately measured and also the amount of injected fuel is under strict control in response to the air amount. However, actually, the air amount and the fuel amount can fluctuate due to various reasons. Accordingly, the actual air fuel ratio deviates from the objective air fuel ratio.
Some of the reasons are as follows:
That is, whole of the injected fuel may not be mixed with an air charge. A part of the fuel adheres on an inner wall of the air intake passage. Such adhered fuel evaporates sooner or later. However, the amount of evaporation of the fuel depends on the time constant of evaporation that is determined with the temperature of the inner wall of the air intake passage (hereunder referred to as xe2x80x9cintake wall temperaturexe2x80x9d) and other running conditions of the engine. Also, the rate of adhesion of the fuel on the inner wall fluctuates in response to changes in the running conditions. Hereunder, therefore, the amount of the fuel that is injected will be referred to as xe2x80x9cinjected fuel amountxe2x80x9d and the amount of the fuel that is actually burnt will be simply referred to as xe2x80x9cfuel amountxe2x80x9d. Further, the air amount fluctuates with changes in environmental conditions that occur, for example, in the intake temperature and the atmospheric pressure surrounding the engine, and moreover aging (deterioration with age) of the engine per se such as a kind of disorder of valve timings.
In order to resolve the problems noted above, one idea is proposed in the U.S. patent application Ser. No. 08/949,838, U.S. Pat. No. 5,954,783. This application discloses a control system wherein a control device is provided which has a learning model for figuring out a presumed air amount and a presumed fuel amount to be learned in response to engine running conditions. The learning model is formed with, for example, a fuzzy neural network. The control device learns, on a real-time basis or an on-line basis, the presumed air amount and the presumed fuel amount based upon the difference between the objective air fuel ratio and the actual air fuel ratio and then controls the fuel amount in a feed-forward control manner. The control method, thus, deals well with the problems occurring from the deviation between a theoretical amount and an actual amount, the transitional conditions, the changes in environmental conditions and the aging. The learning on the real-time basis or the on-line basis will be referred to as xe2x80x9con-line learningxe2x80x9d hereunder.
However, in this conventional control system, when environmental conditions surrounding the engine change violently, a large difference occurs in control between using a leaned part and using a not-learned part because the control device can only learn a part in which educator data (engine control conditions) have been already obtained.
This problem will be described with reference to FIGS. 1A and 1B.
FIGS. 1A and 1B illustrates a couple of three dimensional graphs showing results of learning as to the relationships among the engine speed N, the throttle valve opening and the volumetric efficiency Ve. The volumetric efficiency means a volumetric ratio of an induced air charge volume per stroke versus a cylinder volume. Generally, the lower the atmospheric pressure is, the smaller the volumetric efficiency is. Thus, the volumetric efficiency at the summit of a high mountain is smaller than that at the foot of the mountain and at the half of the mountain it is also the half of them. FIG. 1A shows a situation before ascending halfway (5 gohme) of Mount Fuji, while FIG. 1B shows another situation after descending from there to the foot of the same mountain. Because of the differences in loads on the engine between ascending and descending a mountainside, respective ranges, in which the throttle valve opens, are different to each other. Accordingly, the control map that is made after learning of the descending situation is no longer the same one that was made before learning of the ascending situation. Thus, the control device can not figure out accurate air amounts for the appropriate control.
This situation arises because the control device recognizes that the drop in atmospheric pressure is a kind of aging or a semi-permanent change because the change continues for relatively a long period and then modifies the control mode to be adapted to this changed environment. In addition to this, the on-line learning method rewrites a control map every moment. The renewal of the map occurs not only as to the changed condition but also as to other conditions relating to the changed condition. Further, once the renewal is completed, it is not easy to return to the previous state even though the given condition is removed.
These are problems of the control system using the on-line learning model, although it has a number of advantages.
Although the problems are described above in connection with the fuel injection control of the engine, other controls may have the same problems. For example, in a robot control, temporary changes in xe2x80x9cemotionxe2x80x9d of a robot can exert influence on the control of xe2x80x9cpersonalityxe2x80x9d of the robot if the temporary changes continue for a relatively long period of time.
It is, therefore, a principal object of this invention to resolve the abovenoted problems in conventional control systems.
In order to resolve the problems, there would be one idea wherein an adjustment control as to environmental changes in a relatively short period is provided in addition to a basic control (corresponding to the conventional control) as to partial changes including aging in a relatively long period. However, the adjustment control and the basic control are likely to interfere relative to each other.
It is, therefore, another object of this invention to provide a control system whereby the interference of a basic control with an adjustment control is almost nothing or the minimum so that undesirable biased control will be precluded.
In accordance with one aspect of this invention, a method is for controlling performance of a machine by a control system, which machine is operable by a causative signal, the performance of which machine is indicatable by an indicative signal, wherein the indicative signal outputted from the machine deviates from a pre-set target value of the indicative signal due to an internal change and an external change of the machine while operating the machine.
The control system comprises;
(i) a control unit programmed to output a causative signal when receiving pre-selected signals, wherein the input-output relationship of the control unit is regulated by control parameters;
(ii) a parameter-outputting unit programmed to output a control parameter to the control unit at a parameter-outputting unit connection when the parameter-outputting unit receives pre-selected signals; and
(iii) a compensation-outputting unit programmed to output a compensation signal to the control unit at a compensation-outputting unit downstream of the parameter-outputting unit connection when receiving pre-selected signals.
The method comprises the steps of:
(a) detecting a discrepancy between the indicative signal outputted from the machine and the pre-set target value of the indicative signal;
(b) modifying the control parameter to compensate for the detected discrepancy, whereby the internal change in the machine is compensated for; and
(c) modifying the compensation signal to compensate for the detected discrepancy, whereby the external change of the machine is compensated for.
In accordance with another aspect of this invention, a control system is for controlling performance of a machine, which machine is operable by a causative signal, the performance of which machine is indicatable by an indicative signal, wherein the indicative signal outputted from the machine deviates from a pre-set target value of the indicative signal due to an internal change and an external change of the machine while operating the machine.
The control system comprises;
a control unit programmed to output a causative signal when receiving pre-selected signals, wherein the input-output relationship of the control unit is regulated by control parameters;
a parameter-outputting unit programmed to output a control parameter to the control unit at a parameter-outputting unit connection when the parameter-outputting unit receives pre-selected signals, wherein the input-output relationship is regulated by coefficients, the coefficients being adjusted to modify the input-output relationship to compensate for a discrepancy between the indicative signal outputted from the machine and the pre-set target value of the indicative signal, whereby the internal change in the machine is compensated for; and
a compensation-outputting unit programmed to output a compensation signal to the control unit at a compensation-outputting unit downstream of the parameter-outputting unit connection when receiving pre-selected signals, wherein the input-output relationship is regulated by coefficients, the coefficients being adjusted to modify the input-output relationship to compensate for a discrepancy between the indicative signal outputted from the machine and the pre-set target value of the indicative signal, whereby the external change of the machine is compensated for.